Cu Doping Regulates the Local Structure of CoAl Layered Double Hydroxides for Enhanced Photocatalytic Nitrogen Fixation

Layered double hydroxides (LDHs) have attracted considerable interest in photocatalytic nitrogen fixation owing to their tunable composition and layered structure; however, their photogenerated carrier utilization efficiency and electron-donating capability remain limited. In this work, a series of Cu-doped CoAl-LDH photocatalysts were constructed by introducing Cu as a heterodopant, and the effects of Cu incorporation on the structural features, electronic properties, and photocatalytic nitrogen fixation performance were systematically investigated. Structural characterizations reveal that Cu is predominantly incorporated into the LDH lattice by substituting Co sites, effectively modulating the local Co–O coordination environment while preserving the overall crystalline framework. Electronic structure analyses demonstrate that Cu doping enhances visible-light absorption and induces an upward shift of the Fermi level accompanied by a reduced work function, thereby lowering the energetic barrier for photogenerated electrons to participate in N 2 reduction. Electrochemical and spectroscopic results further confirm that Cu doping markedly improves charge separation and transport behavior. Benefiting from the synergistic optimization of structural and electronic properties, the 3% Cu-CoAl-LDH sample exhibits the highest photocatalytic nitrogen fixation activity, with an NH 4 + generation rate approximately 2.5 times that of the undoped counterpart. This work highlights heterometal doping as an effective strategy to regulate local coordination environments and electronic structures for enhancing the photocatalytic nitrogen fixation performance of LDH-based materials.